1. Field of the Invention
The present invention relates to a control apparatus for an internal combustion engine for changing a cam phase with respect to a crank shaft.
2. Description of the Related Art
Conventionally, there is known a control apparatus for an internal combustion engine including: an oil pressure regulating valve having a solenoid; a variable cam phase mechanism for changing a cam phase with respect to a crank shaft by operating the oil pressure regulating valve; and a control unit for controlling the oil pressure regulating valve, the control unit including: actual cam phase detecting means for detecting the cam phase by inputting a crank angle from a crank angle sensor and by inputting a cam angle from a cam angle sensor; target cam phase setting means for setting a target cam phase with respect to the crank shaft according to a drive condition; feedback control means for outputting a duty for operating the oil pressure regulating valve so that the above-mentioned cam phase is made coincident with the above-mentioned target cam phase to perform PID feedback control of the cam phase; and learning value calculating means for learning the output duty in the case where the above-mentioned cam phase becomes a predetermined value as a learning value (refer to, for example, JP 2001-234765 A).
In the above-mentioned control apparatus for the internal combustion engine, for instance, when an ignition key is turned ON, the feedback control means commences a PID feedback control of a cam phase, while such a learning value which has already been learned is employed as an initial value of an integral term of the feedback control means.
However, in the above-mentioned control apparatus for the internal combustion engine, the learning value which is set as the initial value of the integral term corresponds to such a value of the output duty that the learning value calculating means learned in the case where the cam phase has become the predetermined value as the learning value in the past, but this learning value is not equal to a learning value corresponding to temperature of a coil in the case where the PID feedback control is commenced by the feedback control means. As a result, there is such a problem that a response characteristic of the PID feedback control is deteriorated.